The car actually recognized the new TPM... the screen gave the option to Reset or Cancel and told me I could only reset at a full stop. I pulled over, the RESET option then became available, and after accepting that option, it said the TPM would set in about 10 minutes after I started driving... as soon as I started moving, the tires on the screen turned GREEN, and that was it!

I went with the 18's. I'm not going to drive in heavy snow, and I did not want that small of a wheel/profile.